Controlled collisions for multi-particle entanglement of optically trapped atoms

Entanglement lies at the heart of quantum mechanics, and in recent years has been identified as an essential resource for quantum information processing and computation. The experimentally challenging production of highly entangled multi-particle states is therefore important for investigating both fundamental physics and practical applications. Here we report the creation of highly entangled states of neutral atoms trapped in the periodic potential of an optical lattice. Controlled collisions between individual neighbouring atoms are used to realize an array of quantum gates, with massively parallel operation. We observe a coherent entangling-disentangling evolution in the many-body system, depending on the phase shift acquired during the collision between neighbouring atoms. Such dynamics are indicative of highly entangled many-body states; moreover, these are formed in a single operational step, independent of the size of the system.     

Action d'une dose unique de rayons X,administrée en irradiation totale ou locale,sur les acides nucléiques de la moelle osseuse chez le rat blanc

Summary The biochemical effects on bone marrow of a same dose of X rays (700 r) induced by a total body irradiation or a local irradiation are compared. The ribonucleic acid and the desoxyribonucleic acid of bone marrow show a fall during days 2 to 14 after irradiation, followed by complete recovery on day 21. A significant difference is noted during this period between animals exposed to a total or local irradiation system. The changes consecutive to X rays induced by a total irradiation are prominenter and remain longer than in local irradiation. The direct effect of X rays is probably associated with secondary injury of physiological connexions or other substances affected in total body irradiation.

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Travail effectué avec le concours matériel de l'Institut National d'Hygiène.     

Seasonal changes in the levels and the turnover of brain serotonin and noradrenaline in the European hamster kept under constant environment

Summary Seasonal changes in the content and the turnover of noradrenaline and serotonin are shown in various parts of the brain of the European hamster kept under constant conditions of light and temperature.     

Genetic linkage between X-chromosome markers and bipolar affective illness

A pedigree study shows close linkage of bipolar affective illness (manic depression) to the X-chromosome markers colour blindness and glucose-6-phosphate dehydrogenase deficiency. The maximum lod score ranges from 7.52 (assuming homogeneity) to 9.17 (assuming heterogeneity); that is, the odds in favour of linkage range between 3 X 10(7) to 1 and 10(9) to 1. These results provide confirmation that a major psychiatric disorder can be caused by a single genetic defect. As a possible first step in characterizing the primary genetic abnormality, this finding may have important implications for the aetiology, nosology, pathophysiology and, possibly, prevention and treatment of bipolar affective disorder. It also provides a means for identifying and characterizing homogeneous populations of patients and may help in clarifying aetiological heterogeneity.     

Regulation of phyllotaxis by polar auxin transport

The regular arrangement of leaves around a plant's stem, called phyllotaxis, has for centuries attracted the attention of philosophers, mathematicians and natural scientists; however, to date, studies of phyllotaxis have been largely theoretical. Leaves and flowers are formed from the shoot apical meristem, triggered by the plant hormone auxin. Auxin is transported through plant tissues by specific cellular influx and efflux carrier proteins. Here we show that proteins involved in auxin transport regulate phyllotaxis. Our data indicate that auxin is transported upwards into the meristem through the epidermis and the outermost meristem cell layer. Existing leaf primordia act as sinks, redistributing auxin and creating its heterogeneous distribution in the meristem. Auxin accumulation occurs only at certain minimal distances from existing primordia, defining the position of future primordia. This model for phyllotaxis accounts for its reiterative nature, as well as its regularity and stability.